Conventionally, in accordance with a decrease in the sizes of electronic devices, electrical devices, and the like, efforts have been made to decrease the sizes and the thicknesses of electronic and electrical components such as terminals, connectors, relays, and the like that are used in the electronic devices, the electrical devices, and the like. Therefore, there is a demand for a copper alloy that is excellent in spring properties, a strength, and a conductivity as a material which constitutes the electronic and electrical components. Particularly, as described in Non-Patent Document 1, it is preferable for the copper alloy that is used in electronic and electrical components such as terminals, connectors, relays, and the like to have a high proof stress and a low Young's modulus.
As a copper alloy that is excellent in spring properties, a strength, and a conductivity, a Cu—Be alloy containing Be is provided in, for example, Patent Document 1. This Cu—Be alloy is a precipitation-hardened alloy with a high strength, and CuBe is age-precipitated in a matrix phase; and thereby, the strength is improved without decreasing the conductivity.
However, the Cu—Be alloy contains an expensive element of Be; and therefore, the cost of raw materials is extremely high. In addition, when the Cu—Be alloy is manufactured, toxic beryllium oxides are generated. Therefore, in the manufacturing process, it is necessary to provide a special configuration of manufacturing facilities and strictly manage the beryllium oxides in order to prevent the beryllium oxides from being accidentally leaked outside. As described above, the Cu—Be alloy had problems in that the cost of raw materials and the manufacturing cost were both high, and the Cu—Be alloy was extremely expensive. In addition, as described above, since a detrimental element of Be was included, the use of the Cu—Be alloy was avoided in terms of environmental protection.
For example, Patent Document 2 proposes a Cu—Ni—Si-based alloy (so called Corson alloy) as a substitute material that replaces the Cu—Be alloy. This Corson alloy is a precipitation-hardened alloy in which Ni2Si precipitates are dispersed, and the Corson alloy has a relatively high conductivity and a strength, and also has stress relaxation property. Therefore, the Corson alloy is frequently used for terminals for automobiles, small terminals for signal systems, and the like, and development thereof is actively performed.
In addition, as other alloys, a Cu—Mg alloy disclosed in Non-Patent Document 2, a Cu—Mg—Zn—B alloy disclosed in Patent Document 3, and the like have been developed.
With regard to the Cu—Mg-based alloy, as can be seen from a phase diagram of Cu—Mg system shown in FIG. 1, in the case where the content of Mg is 3.3 atomic % or more, intermetallic compounds including Cu and Mg can be precipitated by performing a solution treatment (from 500° C. to 900° C.) and a precipitation treatment. That is, even in the Cu—Mg-based alloy, a relatively high conductivity and a strength can be obtained through precipitation hardening as is the case with the above-described Corson alloy.
However, in the Corson alloy disclosed in Patent Document 2, the Young's modulus is relatively high, that is, 125 GPa to 135 GPa. With regard to a connector having a structure in which a male tab pushes up a spring contact portion of a female terminal and is inserted into the female terminal, in the case where the Young's modulus of a material that constitutes the connector is high, there is a concern that a variation in contact pressure during the insertion becomes large, and the contact pressure easily exceeds an elastic limit; and thereby, plastic deformation occurs. Therefore, it is not favorable.
In addition, in the Cu—Mg-based alloys disclosed in Non-Patent Document 2 and Patent Document 3, similarly to the Corson alloy, the intermetallic compounds are precipitated. Therefore, there is a tendency that the Young's modulus becomes high, and thus as described above, it is not favorable as a connector.
Furthermore, since coarse metallic compounds are dispersed in a matrix phase, the intermetallic compounds serve as a starting point of cracking during a bending process, and thus the cracking occurs easily. Therefore, there is a problem in that it is difficult to form a connector having a complicated shape.